Furnace roof or arch



April s, 1952 J, E, PLUCK 2,592,184

FURNACE Roo?l 0R ARCH Filed April 23, 1948 2 SHEETS-SHEET l fo/1w.FDA/HRD PL ack HUMA/f,

Attorney -April 8, 1952 J. E. PLUCK FURNACE ROOF 0R ARCH Filed April 25,194e 2 SHEETS-SHEET 2 Q5 Q a N "0 O h n Q .Q x, I

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f i l :i 0 l/ l 'Ak il v 2 il N f N O /Il /nventor .7o/,w EDA/,ofen PLUCK Patented Apr. 8, 1952 FURNACE ROOF OR ARCH John Edward Pluck,Rotherham, England Application April 23, 1948, Serial No. 22,781 InGreat Britain April 29, 1947 8 Claims.

This invention relates to the roofs or arches of industrial furnaces foruse at high temperatures, which are built up `of bricks of refractorymaterial, particularly to the roofs or arches of tilting furnaces ofthis type. The normal roof` material for such furnaces is silica, whichpossesses the property of almost completing its thermal expansion below600 C., with the result that the temperature fluctuations encountered innormal working cause substantially no alteration in the shape orcondition of the roof. In the construction of open hearth basic steelfurnaces the use in place of silica of basic refractory materials, suchas chrome magnesite, is very desirable on metallurgical grounds. Owingto the substantially linear thermal expansion of these basicrefractories, the temperature fluctuations encountered in practice causenot only expansion and contraction of the roof but also substantialincrease and decrease of its radius of curvature. Various proposals havealready been made for supporting roofs of basic refractory material insuch a way as to accommodate the movement produced by temperaturevariations.

In the specification of the prior United States Patent 2,444,365 of theinventor herein, there is described a construction for a stationaryfurnace in which the roof buttresses are attached to the lower ends of apair of pivoted levers whose upper ends are coupled together through areversing lever and a tie rod, so that the buttresses move equally andoppositely. The upper end of the lever carrying the rear buttress isconnected to the short arm of a bell crank lever which is pivoted to afixed point and has a weight bar hung from its longer arm. The4arrangement is such that the leverage of the weight varies with theposition of the roof, so that the varying roof thrust is balanced (witha margin of safety) at all temperatures in the working range.

According to the present invention a construction which is in generalsimilar to that described in the above mentioned patent specification ismodified for use in tilting furnaces. The invention comprises a tiltingfurnace having a roof of basic refractory material, in which the roofbuttresses are attached to the lower ends of a pair of pivoted leverswhose upper ends are coupled together in such a way that the buttressesmove equally and oppositely and are also couj pled to a lever arm fromwhich there is suspended a weight for balancing the roof thrust, theweight lever arm being inclined to the horizontal when the furnace isupright, so that when the furnace is tilted the weight lever arm willmove towards the horizontal and the leverage of the weight willautomatically be increased to balance the increased load in the roof.

Other and further objects, features and advantages of the invention willbe pointed out hereinafter and set forth in the appended claims formingpart of the application.

In the accompanying drawing a now preferred embodiment of the inventionis shown by way of illustration and not by way of limitation.

In the drawing:

Fig. 1 is a vertical section through a furnace according to theinvention in its upright position, and

Fig. 2 is a section similar to Fig. l showing a furnace in its tiltedposition.

The furnace proper comprises a bath receiving lined receptacle I6 with atap spout I'I and a roof or arch 4. The receptacle is cradled in afurnace support structure generally designated by I8. The structure iscarried on arcuate base members I, which are supported on rollers 2, sothat the furnace can be tilted (clockwise in the drawing) by means of anhydraulic jack 3 operatively coupled with support structure I8 and abase I9. Fig. 2 shows clearly the positions of the various parts in thetilted position of the furnace. The ends of the furnace roof 4, areengaged by buttresses 5, attached to the lower ends of a pair of pivotedlevers 6, whose pivot points are so chosen as to allow for boththeexpansion and contraction and the change in shape of the roof causedby temperature changes. The upper ends of levers 6 are coupled togetherthrough a reversing lever 1 and a tie rod 8 and the upper end of thelever 6 carrying the rear buttress is connected to the shorter arm of abell crank lever 9 pivoted by means of a pivot I3 to the top of supportstructure I8. From the longer arm of this lever there is suspended a bar2U carrying weights I0 which are adjusted to balance the roof thrustwith a suitable margin of safety, some of the weights being removed asthe roof thins with use. The tie rod 8 is also connected through bellcrank leversY and links to rolled steel joists II which bear on theupper surface of the roof and prevent it from collapsing outwards.

The arm of bell crank lever 9 from which the weights bar 20 is suspendedis inclined upwardly and rearwardly when the furnace is in the uprightposition illustrated, so that when the furnace is tilted towards the taphole side as can best be seen on Fig. 2, the distance between the lineof action of the weight and the fulcrum point of the lever isautomatically increased to a balance the increased load in the roof. Inthe particular design of furnace illustrated, in which the includedangle of the roof (in the hot condition shown in Fig. 1 in full lines)is approximately 60 and the tilting angle is approximately 30, the loadincrease on tilting was found to be about 15%. The increased pressure onthe buttresses necessary to balance this increased load could thus beobtained by inclining the weight lever arm upwardly at an angle ofapproximately 30 to the horizontal.

With such an arrangement, if the weight bar were suspended from a fixedpoint on the lever arm, a movement of the roof towards its cold position(shown in Fig. 1 in dotted lines) would result in an increase in thepressure applied to the buttresses, instead of the decrease in pressurerequired to balance the roof load. Accordingly, the effective length orthe arm of crank lever 9 from which the weight I0 is suspended is made'-variable'corresponding to the roof movements due to temperature changes.For this purpose the aforesaid lever arm is provided with an elongatedslot ld, and a cam plate l2 having an appropriate elongated slot l5 isxedly secured to support structure in a position parallel tothe plane ofmovement of lever The weight bar 20 is suspended by means of a pin 2lwhich is passed through both said slots. As will be evident, a variationof the angular position of the lever relative to structure le due totemperature caused roof movements will result in a displacement of thepin within the slots and hence in a corresponding change in theeffective length of thelong; arm of lever e. Fig. l shows in full linesthe weight suspension for a hot roof and the dotted lines the weightsuspension for `a cold roof. It will further be evident that by suitableshaping and positioning of slots le and l5, the position of thesuspension pin and hence of the weight can be automatically so adjustedthat the weightv always produces the neces-- sary balancing pressure on;the buttresses.

In the construction illustrated, the levers 5 supporting the buttressesand the bell crank'lever e and reversing lever 'i connected to theirupper ends are pivotally supported upon the bach and front wall stays,that is to fixed parts of the furnace. Alternatively, however, thepivots of these levers may be suspended for vertical sliding movement asdescribed in the above mentioned patent specification. Y

What is claimed is:

l. An industrial furnace tiltable from an upright position into aninclined position having a bath receiving receptacle and a roof of basicrefractory material engaged at its ends by buttresses attached tothelower ends jof apair of pivotal levers coupled together attheir upperends by linkage means causing the buttresses to move equally andoppositely in response to movements of the roof due to temperaturechanges, in combination `with support Ameans providing for tilting thefurnacek with the receptacle and the roof from an upright position intoan inclined position relative to' thesupport means, level meanssecured-to the linkage jmeans and to the furnace for angularv movementtogether with the latter, said lever meansbeing positioned upwardlyinclined to the `horizontal when the furnace is in its uprightposition,and a counterweight suspended from saidv lever means for balancing theroof-thrust on the buttresses, tilting of the furnace moving the levermeans toward the horld zontal, thereby increasing the leverage of saidcounterweight.

2. An industrial furnace as described in claim l, in combination withweight suspension means displaceable along the lever axis of said levermeans, and adjustment means lixedly secured to the furnace and engagingsaid suspension means for varying the position thereof relative to thelever axis in response to a change in the position of the lever meanscaused by roof movements due to temperature changes, thereby varying theweight leverage in accordance with the roof movements and automaticallybalancing the variations of the roof pressure upon the buttresses ascaused by said roof movements due to temperature changes.

3.. An industrial furnace as described in claim 2, wherein saidadjustment means comprise a cam member iixedly mounted on the furnacefor a tilting movement in unison with a tilting movement of the furnaceand engaging said suspension means for displacing the sameincorrespondence with the aforesaid roof movements due to temperaturechanges.

v4:. An industrial furnace as described in claim 3, wherein said levermeans comprise aleverv arm having an axial elongated slot, and whereinsaid cam member comprises a cam plate mounted substantially parallel tothe plane of said lever arm and including an elongated slot positionedat an angle to the lever slot, and wherein said suspen-l sion meanscomprise a Ipin elementvsupporting the counterweight andengagingsaid/slots, the relative angular position of the slotscontrolling the position of the pin elementin the lever vslot and,hence, the leverage of said counterweight; 1^"

5. An industrial furnace of thevtype comprising a bath receivingreceptacle, `a furnace support structure, a roof arch associatedtherewith, supporting levers at opposite ends of said arch, buttressesfor said arch received 4by one end of each of said levers, pivot meansintermediate the ends of said levers for pivoting the same to thefurnace support structure, suspension means connected to said levers forsupporting the same and the arch from said furnace support structure,and connecting means lconnecting the ends of said supporting leversopposite the arch receiving ends for accommodating inward and outwardmovements of said arch ends withrespect to each other due to expansionand contraction'of the arch, in combination with supportmeans providingfor tilting the'furnace support structure with the receptacle and theroof from an upright position relative to the support means into aninclined position, lever means pivoted to the furnace support structureand coupled to said con# necting means, the angular position of saidlever means relative to the furnace being controlled by movements of theconnecting means as caused by expansions and contractions of the roofarch, and relative to the horizontal by the position of tilt of thefurnace support structure, the said lever means being in an upwardlyinclinedv position when the furnace support structure is in its uprightposition, and a counterweight suspended from said lever means forbalancing the roof thrust on the buttresses, tilting of thefurnacesupport structure moving the lever means toward the horizontal, therebyincreasing the leverage of the counterweight when the furnace supportstructure is tilted from its upright position into an inclined position.l

6. An industrial furnace Ias defined in claim 5, wherein said levermeans comprise a bell crank,

one arm of said bell crank being pivoted to said connecting means andthe other arm supporting said counterweight.

'7. An industrial furnace as dened in claim 5, in combination withcompensating means compensating for variations in thrust upon saidbuttresses as caused by expansions and contractions of the roof arch,the said compensating means comprising suspension means for saidcounterweight and a member xedly secured to the furnace supportstructure for tilting in unison therewith, said lever means and said xedmember each having bearings slidably engaged by said suspension meansfor supporting the latter, the position of the suspension means withinand relative to the bearings determining the effective length of thelever means, and hence, the leverage of the counterweight, the saidposition of the suspension means being controlled by the angularposition of the lever means relative to the furnace support structure,and, hence relative to the said fixed member.

8. An industrial furnace as defined in claim '7, wherein said levermeans comprise a lever arm having an axially elongated slot, and whereinsaid fixed member comprises a cam member mounted substantially parallelto the plane of 6 said lever arm and including an elongated slotpositioned at an angle to the slot in the lever arm, and wherein saidsuspension means com- Y prise a pin element supporting the counterweightand engaging said slots. the relative angular position of the slotsbeing controlled by the angular position of the lever means relative tothe furnace support structure and, hence, relative to the cam member andcontrolling the position of the pin element in the lever slot, therebyalso controlling the leverage of said counterweight.

JOHN EDWARD PLUCK.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

